A Submarine for Saturn's Moon Titan? NASA Backs Way-Out Ideas

Image: Saturn as seen from Titan

An artist's conception shows Saturn in the sky above a hydrocarbon lake on Titan. To the human eye, the atmosphere is opaque, but in the infrared there are "windows" where the atmosphere is more transparent, as indicated in this artwork. Gregor Kervina / NASA

NASA has approved funding for a dozen way-out science projects, including a proposal for a robotic submarine that could plumb the depths of the hydrocarbon lakes on Titan, a smog-shrouded moon of Saturn.

"It's a very far-out idea, but it's something that I think we can definitely do engineering-wise," Steven Oleson of NASA's Glenn Research Center in Cleveland told NBC News.

The Titan submarine project is just one of 12 proposals selected for study under Phase I of the NASA Innovative Advanced Concepts Program — which is the space agency's equivalent of the Defense Advanced Research Projects Agency, or DARPA.

Image: Titan sub
An artist's conception shows a submarine examining the bottom of one of Titan's lakes. NASA

Phase I grants are worth about $100,000, paid to recipients over the course of nine months. If the initial studies are successful, projects can go on to Phase II and receive up to $500,000 for two more years of concept development.

In the past, NIAC has backed ideas ranging from space elevators to skin-tight spacesuits to suspended animation.

Oleson and his colleagues on Glenn Research Center's COMPASS team have gotten a couple of NIAC grants before, for a Venus landsailing rover and a long-lasting, lithium-powered Venus lander called ALIVE. The team also helped figure out the technologies needed for NASA's plan to capture a near-Earth asteroid.

"My group did that in 2011. ... And son of a gun, what we did in two weeks still looks like what they're planning," Oleson said.

How to build a sub for Titan

The Titan submarine just might be the first probe to dive into a pool of liquid on another celestial body. In this case, the liquid wouldn't be water, but the supercold methane and ethane in Kraken Mare, a 720-mile-long (1,170-kilometer-long) lake. Hydrocarbons that would be gassy on Earth take on a liquid form on Titan, where the surface temperature is 290 degrees below zero Fahrenheit (-179 degrees Celsius).

Titan is thought to be an analog to early Earth, and studying what lies beneath the surface of Kraken Mare could well turn up some scientific surprises.

Oleson's team will use the NIAC grant to figure out what it would take to explore the lake, which is thought to be up to 1,000 feet (300 meters) deep. He'll be working with the project's scientific principal investigator, Ralph Lorenz of Johns Hopkins University's Applied Physics Laboratory, as well as Michael Paul of Penn State's Applied Research Laboratory, an expert on submersible technologies.

"The focus for us is trying to get a vehicle that will operate in a hydrocarbon sea," Oleson said. "Think of it as liquid natural gas. How would you get a vehicle to operate in there?"

The questions to be resolved include how the sub would be powered and propelled.

"Do you use a plutonium-powered system, or do you put a small reactor on it, or do you go non-nuclear and take some oxidizer with you? It's a sea of natural gas, after all," Oleson said. Some sort of gas-powered fuel cell might do the trick, he said.

NASA has already considered a mission called the Titan Mare Explorer, or TiME, which would drop a boat into Titan's seas. A submarine would kick things up a notch, but Oleson emphasized that the research funded by NIAC represents just the very beginning of what's likely to be a decades-long process.

"We would like to do this during Titan's summer, so that means the 2040s," he said.

The 11 other projects

That's the way it works with NIAC grants: They're just meant to get an interplanetary party started. Here's a rundown on the other far-out Phase I projects:

Titan Aerial Daughtercraft: A different team is proposing a mission concept that involves building a small rotorcraft that could be deployed from a balloon platform in Titan's atmosphere. The craft could take pictures, land on Titan's surface to collect samples, and then return to the mothership to deliver its samples for analysis and recharge its batteries for the next trip.

WRANGLER: The Weightless Rendezvous And Net Grapple to Limit Excess Rotation System would use a nanosatellite-based tether system to capture and de-spin asteroids and space debris.

Comet Hitchhiker: A new kind of spacecraft would use tethers to "harpoon" a comet or some other type of passing celestial object, hitch a ride, harvest kinetic energy from the object, and then cut itself loose when it's time to part ways.

The Aragoscope: This novel space telescope system would take advantage of a low-cost disk arrangement and the principles of diffraction optics, with the potential to produce images of the sky that have 1,000 times the resolution of the Hubble Space Telescope.

Swarm Flyby Gravimetry: This mission concept would be to design a spacecraft to release a swarm of small, low-cost probes as it flew past an asteroid or a comet. By tracking the trajectories of those probes, scientists could map the target object's gravity field and make inferences about its composition and structure.

PRIDE: The Passive Radio Ice Depth Experiment would probe the icy layer that covers Europa, one of Jupiter's moons, by analyzing interactions between the ice and high-energy neutrinos from cosmic rays. The same technology could be used for other icy worlds such as Ganymede and Enceladus.

PERISCOPE: The Periapsis Subsurface Cave Optical Explorer would perform photon time-of-flight imaging to map lunar skylights and caves, even to the point of "seeing around corners" deep below the moon's surface.

Quantum inertial gravimetry and ChipSat sensors: A new kind of architecture for interplanetary reconnaissance would study other worlds using gravity-mapping orbiters that send swarms of miniaturized sensor chips down to the surface.

HERTS: The Heliopause Electrostatic Rapid Transit System is a propellant-less propulsion concept that would use the momentum exchange from protons in the solar wind to propel a spacecraft out of the solar system. Theory suggests that the technology could accelerate a spaceship to something like 225,000 mph (100 to 150 km/sec) over a period of months.

Mars Ecopoiesis Test Bed: Researchers would devise a system to put earthly organisms in Martian soil under strictly controlled conditions, to determine whether the Red Planet could sustain terrestrial life.

3-D photocatalytic air processor: This project would create a new type of catalytic converter, powered by the abundant high-energy radiation in space, to generate oxygen for life support.

Update for 10:55 a.m. June 6: I've added references to other members of the Titan sub team, Ralph Lorenz and Michael Paul.